Project Summary Head & neck squamous cell carcinoma (HNSCC) is currently showing clinical response to immune checkpoint inhibitors, but its efficacy is still low at nearly 20% of the recurrent/metastatic patients treated. One immunological strategy to improve upon this low efficacy rate is to target the high mutational burden of HNSCC, particularly those associated with chronic tobacco exposure. We propose to characterize the mutation associated neoantigen landscape of human HNSCC obtained from patients treated with nivolumab in a neoadjuvant setting using both in silico and mass spectroscopy methods to directly obtain these human neo- epitopes. In conjunction with these studies, we will characterize the immunodominant MHC restricted neoantigens in an autologous humanized murine system in vivo. These findings will help direct a novel strategy to expand these neoantigen-specific T-cells using a potent STING agonist formulated nanoparticles with known neoantigens found in human HNSCC. Findings from this proposal will also impact how neoantigen-based cancer vaccines should be administered in conjunction with immune checkpoint inhibitors in future head and neck clinical trials. Lastly, our proposal will also inform neoepitope prediction algorithms and antigen based trials for other cancer types to have deep impact in the field of cancer immunology as a whole.